Spot type disc brakes



July 19, 1966 A. J. WILSON ET AL 3,261,430

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SPOT TYPE DISC BRAKES Original Filed July 11, 1963 ll Sheets-Sheet 7July 19, 1966 Original Filed July 11. 1963 A. J. WILSON ET Al.

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SPOT TYPE DISC BRAKES Original Filed July 11, 1963 ll Sheets-Sheet lllOl 1e .2 l8 i "o m I09 I07 I06 i Ill 7 Egg-L? |7 r E Ill "2 H3 5 {4749K E l lwwam IOI United States Patent 3,261,430 SPOT TYPE DISC BRAKESAlexander John Wilson, Sutton Coldfield, Stewart Kevern Hambling,Tamworth, and Anthony William Harrison, Selly Oak, Birmingham, England,assignors to Girling Limited, Birmingham, England, a British companyContinuation of abandoned application Ser. No. 294,282, July 11, 1963.This application July 1, 1965, Ser. No. 473,550

6 Claims. (Cl. 18873) This application is a continuation of our priorapplication Serial No. 294,282 filed July 11, 1963 and now abandoned.

This invent-ion relates to improvements in disc brakes of the kind inwhich friction pad adapted to engage opposite faces of a rotatable discare associated with a caliper or clamping member which straddles aportion of the disc and carries or incorporates first actuating meansfor urging one friction pad into engagement with one face of the disc,the other friciton pad being urged into engagement with the oppositeface of the disc by second actuating means associated with the caliperor clamping member or by the reaction of the first actuating means onthe caliper or clamping member which cause the caliper or clampingmember to slide or swing relative to the disc.

In the usual brake of this type at least one of the friction pads ismounted on a rigid backing plate located between spaced abutments in thecaliper or clamping member. When the brake is applied the pad tends tomove angularly with the disc and the backing plate is urged against theabutment at its rear end which takes the braking torque on the pad. Thepad then tends to swing in towards the disc, swinging about the rear endof the backing plate as a fulcrum, and the pad behaves in a similarmanner to a leading shoe in an internal shoe drum brake. It is believedthat this effect is the cause of brake squeal which is sometimesproduced when the brake is applied.

According to the present invention, in a disc brake of the kind setforth the torque on at least the actuated pad is taken solely by meanslocated at or adjacent the forward end of a rigid backing plate carryingthe friction pad, that is, the end with which any given point on thesurface of the disc first comes into alignment in the normal directionof rotation of the disc.

According to a further feature of the invention, when the caliper orclamping member moves or swings relative to the disc and a firstfriction pad is urged into engagement with one face of the rotatabledisc by the reaction on the caliper of the actuating means which urgethe other friction pad into engagement with the opposite face of thedisc, the first friction pad is applied to the disc through an adjusterwhich automatically advances the pad relative to the disc in a directiontowards the disc as the pad wears thereby reducing to a minimum themovement of the caliper or clamping member.

Thus when the brake is applied at least the actuated friction pad has noforce acting on it which tends to swing it towards the disc and itbehaves in a similar manner to a trailing shoe in an internal shoe drumbrake and the tendency for the brake to squeal is eliminated or greatlyreduced.

The means for taking the torque at or adjacent to the forward end of thebacking plate and for reducing to a minimum the movement of the caliperor clamping member relative to the disc as the pad wears in the case ofa sliding or swinging caliper or clamping member, may be arranged invarious ways.

3,261,430 Patented July 19, 1966 "ice plane at right angles to a radiusof the disc passing through the centre of the caliper;

FIGURE 2 is a section on the line 22 of FIGURE 1;

FIGURE 3 is a section similar to FIGURE 1, showing a modifiedconstruction;

FIGURE 4 is a section on the line 4-4 of FIGURE 3;

FIGURE 5 is a plan of another form of caliper;

FIGURE 6 is a section on the line 66 of FIGURE 5;

FIGURE 7 is an end view including a fragmentary section through a brakecaliper in the plane of the disc;

FIGURE 8 is an elevation of one side of the caliper shown in FIGURE 7;

FIGURE 9 is a perspective view of another form of brake caliper;

FIGURE 10 is a section through yet another form of brake caliper in aplane parallel to the plane of the disc;

FIGURE 11 is an end view showing one construction for guiding a backingplate;

FIGURE 12 is a view showing guiding means for a backing plate disposedbeyond the inner periphery of the disc;

FIGURE 13 is a perspective view of a guide plate embodied in theconstruction illustrated in FIGURE 10;

FIGURE 14 is an end view of yet another form of brake caliper;

FIGURE 15 is an end elevation including a fragmentary section on theline 15-15 of FIGURE 14;

FIGURE 16 is a plan of the caliper illustrated in FIG- URES 14 and 15;

FIGURE 17 is a section on the line 1717 of FIG- URE 1'8; and

FIGURE 18 is a section on the line 18-18 of FIG- URE 17.

In FIGURES'I and 2, 10 is a caliper of substantially U form adapted tostraddle a portion of the periphery of a brake disc 11, rotating with awheel or other part of a vehicle transmission. The caliper is fixed to anon-rotating part of the vehicle by bolts passing through lugs 12extending inwardly from one limb.

Opposite faces of the disc are adapted to be engaged by friction pads 13bonded to rigid backing plates 14 which are urged towards the disc bypistons 15 working in opposed hydraulic cylinders 16.

When the brake is applied the friction pads tend to rotate with thedisc, and in the construction shown in FIGURES 1 and -2 the torque onthe friction pads is taken by abutments comprising pins 17 screwedthrough lugs 18 on the caliper lim'bs at one end and passing throughopenings in the backing plates which are extended at that end.

The disc rotates in the direction indicated by the arrows in thedrawings and the pins 17 are located at the forward ends of the backingplates, that is the ends which any given point on the braking surface ofthe disc first approaches.

Thus when the brake is applied the friction pads trail from the pins bywhich the torque is taken and behave in a manner similar to a trailingshoe in a shoe drum brake.

In the modification shown in FIGURES 3 and 4 there are torque-takingabutments at each end of the caliper comprising pins 17 passing throughholes in each end of each backing plate. The holes in the backing plateare of such a form as to provide a clearance 19 on the inner side ofeach pin so that in whatever direction the disc is rotating the torqueon the friction pads will be taken wholly by the pins at the ends of thebacking plates with which any given point on the disc first comes intoalignment.

In the two constructions described above, on removal of the pins 17 thefriction pads with their backing plates can be removed and replaced in asubstantially circumferential direction through the end of the caliper.

FIGURES 5 and 6 show the application of our invention to a disc brakehaving a caliper 21 with an opening in its radially outermost side forthe insertion and removal of the friction pads. The caliper is formedfrom two castings secured together at each end by bolts 22, 23. Eachfriction pad 24 is bonded to a backing plate 25 of roughly squareoutline which is anchored adjacent to its outer end by spaced abutmentscomprising parallel pins 26 detachably mounted in the caliper andpassing through holes in the backing plates. These holes provideclearances 27 on the inenr side of the pins to ensure that when thebrake is applied the torque on the friction pad asembly is taken only bythe pin at the forward end.

The inner edge of each backing plate is located by abutments 28 on thecaliper limb engaged by lugs 29 at opposite ends of a recess in theinner edge of the plate.

Inclined bars 31 may be provided on the inner faces of the end parts ofthe caliper to act as scrapers to keep the surface of the disc free frommud in bad weather.

On removal of the pins 26 the pads and backing plates can be withdrawnand insterted through the opening in the radially outer side of thecaliper.

In further modifications actuating means are located in or on one limbof a caliper or clamping member for urging the adjacent friction padinto engagement with a disc and the other pad is brought into engagementwith the opposite face of the disc by the reaction of the actuatingmeans on the caliper or clamping member and the caliper or clampingmember slides or swings relative to the disc.

As shown in FIGURES 7 and 8 a caliper or clamping member comprises arigid member of U-form having spaced limbs 41 and 42 lying on oppositesides of a disc 43 which rotates with a wheel. Each limb extends radallyinwards from a bridge portion 44 which lies outside the periphery of thedisc and the caliper or clamping member is attached to a non-rotatingpart of the vehicle by bolts passing through clearance holes in spacedlugs 45 extending radially inwards from the periphery of the disc.

Opposite faces of the disc 43 are adapted to be engaged by friction pads46 and 47 and the pad 46 bonded to a rigid backing plate 48 is urgedinto engagement with the disc by a piston 50 working in an hydrauliccylinder 51 located in the limb 41.

Alternatively the pad 46 can be applied mechanically by a mechanism 52actuated by the hand brake of the vehicle which also actuate/s anadjuster 115 to compensate for Wear on the pad 46.

The backing plate 48 has at opposite ends opposed lugs 53 extendingradially outwards on each end of the bridge portion 44 and engaging attheir inner edges with locating torque taking plates or keepers 54attached on either side of the bridge portion by bolts 55 (FIGURES 7 and8). The plate 48 is retained against radial movement in either directionby outwardly projecting abutment surfaces 56 engaging with opposedrecesses 57 formed in the inner ends of each lug 53. On removal of oneof the locating plates or keepers 54, the backing plate and pad assemblycan be removed in a circumferential direction through the open end ofthe caliper or clamping member after moving the assembly radiallyinwards to disengage the other end of the backing plate from the otherlocating plate or keeper, which may be fixed or may also be detachablysecured to the caliper or clamping member.

The locating plates or keepers 54 are arranged to take the torque on thefriction pad and this is an advantage where the caliper or clampingmember is made of light alloy or other material with poor resistance tofretting as the locating plates or keepers can be made of steel or otherhard material. Alternatively, where the caliper or clamping member ismade of a wear-resisting material, the locating plates or keepers 54 maybe recessed into the ends of the caliper or clamping member so that thebacking plates bear directly on the caliper or clamping member.

In a further embodiment as illustrated in FIGURE 9, a detachable torquetaking plate or keeper 5? is attached on one end of the bridge portion144 of a clamping member 140 by a bolt 59 and has a recess 60 at itsfree end which co-operates with a peg 61 provided on the bridge portion.The backing plate 48 to which the friction pad 46 is bonded has atopposite ends opposed lugs 64 extending radially outwards and havingrecesses 65 formed in their inner ends, one of which is adapted toreceive abutment surfaces of the plate or keeper 58 when the pad ispositioned Within the caliper or clamping member 140. The recess in theother lug 64 receives a similar member attached to the other end of thebridge portion which may be fixed or may also be detachably secured tothe bridge portion as described above.

The plate or keeper 58 is rectangular in section and is provided withtwo unrelated surfaces 158, 160. The surface 16th is adapted toco-operate with a complementary surface 165 in the recess 65 in the lugof the backing plate for taking the circumferential component of torqueon the backing plate in the application of the brake.

The radial component of the braking torque is taken by a surface on thekeeper attached to the other end of the bridge portion of the caliperwhich corresponds to the surface 160. The radial component istransferred to this surface from a complementary surface 166 in therecess 65. It will be appreciated that in the application of the brakethe circumferential component of torque is of a substantially greatermagnitude than that of the radial component, and the area of eachsurface is chosen in accordance with the magnitude of each particularcomponent of torque.

On removal of the detachable plate or keeper 58 by removal of the bolt59, the backing plate and pad assembly can be removed in acircumferential direction through the open end of the caliper orclamping member as described above.

In another embodiment the backing plate may have at opposite endsparallel lugs extending radially outwards and engaging slidably withmachined parallel guiding and torque taking surfaces on the bridgeportion of the caliper or clamping member. With that arrangement the padcan be retained against moving radially inwards by a pin parallel to theaxis of the disc and passing through openings in the lugs on the backingplate and detachably fixed in bosses or equivalent parts on the bridgeportion.

Alternatively the backing plate may have a single central radiallyprojecting lug which is received in a slot in the bridge portion of thecaliper or clamping member and is retained by any convenient means.

The advantage of our constructions described above with reference toFIGURES 79 of the drawings, is that torque take-off is independent ofthe extent of Wear on the friction pads which is particularly importantas the actuated pad 46 has to move through a distance sufficient toaccommodate the wear on both pads.

In these constructions the non-actuated friction pad 47 which is appliedby the reaction on the caliper or clamping member 40 or 140 may bebonded or otherwise secured to its adjacent limb 42 or 142 of thecaliper or clamping member or it may be mounted on a backing plate 49which is guided on the bridge portion 44 or 144 in the same way as theactuated pad 46.

FIGURE 10 shows a brake in which a disc is carried by and rotates with ashaft and a floating or sliding caliper or clamping member 72 straddlesthe outer periphery of the disc. The backing plate 73 has at oppositeends opposed lugs 74 which extend beyond the outer periphery of thedisc.

Recesses 75 are provided at the inner ends of the lugs 74 and one of therecesses is engaged by one end 77 of an abutment surface formed on atorque taking plate 76 attached to one end of the caliper or clampingmember by a bolt 78. The guide plate (FIGURE 13) is formed withresilient extending fingers 79 which are curved and cranked to bearresiliently on the backing plate 73 and the caliper or clamping memberrespectively to prevent rattle.

The other recess 75 may be engaged by an abutment surface of a similartorque taking guide plate or alternatively this recess may be engaged bya fixed torque taking abutment 80 carried by the caliper or clampingmember.

In the application of the brake with the disc rotating in a counterclockwise direction the circumferential component of the braking torqueis taken by the surface 180 on the abutment 80 carried by the caliperwhilst the radial component of torque at the opposite end of the backingplate is taken by the surface 176 on the abutment 75 carried by theopposite end of the caliper. With the disc rotating in the oppositedirection the circumferential component is taken by the surface 175 ofthe abutment 75 and the radial component is taken by the surface 181.

As shown in FIGURE 11, the recesses 75 may be pro vided in the outerends of the lugs 74 and in this construction one abutment end 81 of eachtorque taking guide plate 82 engages with each recess and the guideplates are secured to the caliper or clamping member by bolts 83.

When the disc comprises a ring extending inwardly from a wheel rim or abell housing and the caliper or clamping member straddles the innerperiphery of the disc, lugs 84 on backing plate 85 carrying the directlyactuated pad 86, will extend inwardly beyond the inner periphery of thedisc (FIGURE 12).

With the construction described above, in which the indirectly actuatedpad 47 is applied to the disc by axial or angular movement of thecaliper or clamping member 40, this movement increases the wear of thefriction pads and clearances sufficient to allow for this movement haveto be provided between the disc and between the caliper or clampingmember and a wheel or other member by which the disc is carried. It istherefore desirable, in installations where the space available islimited, to reduce this movement of the caliper or clamping member to aminimum and this is achieved by mounting and guiding the indirectlyactuated friction pad 47 in the limb of the caliper or clamping memberin such a way that its position is automatically adjusted to take upwear.

In one convenient arrangement as illustrated in FIG- URES 14, 15 and 16the pad is backed by a member 90 having a stem 91 of which the axis isparallel to that of that disc 92 and which is guided to slide in a bore93 in the caliper limb 94. The outer end of the stem is screwthreadedand works through a rotatably anchored nut 95 having peripheral ratchetteeth 96, the teeth are engaged by a resilient pawl 97 on a rod 98guided for reciprocal movement in a direction at right angles to theaxis of the stem and moving with a hand lever 99 for actuating the brakeso that the nut 95 is rotated step-by-step to adjust the position of theindirectly actuated pad 47 when the movement of the rod in theapplication of the brake exceeds a predetermined value.

In another construction shown in FIGURES 17 and 18 the indirectlyactuated pad 47 is applied to the disc 100 through an automatic adjusterwhich advances the pad relative to the caliper or clamping member 101 ina direction towards the disc as the pad wears. The indirectly actuatedpad 47 is carried by a rigid backing plate 49 which is engaged by ascrew-threaded stem or spindle 102 screwed into a tapped bore 103 inadjacent limb 104 of the caliper or clamping member 101, the axis of thestem being substantially at right angles to the plane of the disc.

A peripheral toothed ratchet wheel 105 is mounted on the stem adjacentto its inner end and is engaged by a pawl 106 formed at the free end ofa resilient finger 107 pivotally mounted adjacent to its outer end on apin 108 carried by a mounting frame 109 fixed to the caliper, the axisof the pin being at right angles to the axis of the stem.

A projection 110 on the finger offset from the pivot is held inengagement with a stationary abutment 111 by a spring 112 which may bean integral part of the finger bearing on an abutment 113 on themounting frame.

Movement of the caliper relative to the stationary abutment 111 rocksthe finger 107 angularly about its pivot and if the movement of its freeend exceeds the spacing between adjacent teeth on the ratchet wheel 105,the screwed stem 102 is rotated through one or more steps to move theindirectly actuated pad 47 towards the dis-c to compensate for wear ofthe pad.

Any convenient means may be provided for maintain ing a minimumclearance between the friction pad and the disc. For example, a certaindegree of lost motion may be provided between the ratchet wheel 105 andthe stem 102 or at any convenient point in the mechanism.

The mounting frame 109 on which the finger 107 is pivoted is preferablyitself mounted on the caliper adjacent to the indirectly actuatedfriction pad 47 so that the adjustment is not sensitive to deflection ofthe caliper under load.

The mounting frame may also form the means for retaining the frictionpads in position so that removal of plate ,114 for replacement of thefriction pads automatically frees the finger from the ratchet wheel 105and the screwed stem 102 can be readily returned to its initialposition.

Angular movement of the stem 102 except by the advancing ratchetand'pawl mechanism can be prevented by providing any convenientfrictional resistance to such movement, such a ratchet device which maybe stepless, or a detent device.

Temperature sensitive means may be incorporated in the mechanism toprevent over adjustment owing to thermal distortion. For example, theresilient finger 107 may be of bimetallic material so that it deflectsclear of the ratchet wheel when heated beyond a certain temperature andthe adjuster becomes inoperative.

The advantage of our last two constructions described above is thatreduction in the movement of the caliper or clamping member allows theclearance between the caliper or clamping member and the disc to bereduced, with a consequent reduction in the stressed length of thecaliper bridge portion 44 and a reduction in the deflection of thecaliper or clamping member under load.

Where a wear adjuster 115 (FIGURE 7) is incorporated in the actuatingmeans the two adjusters may be coupled together.

We claim:

1. A disc brake comprising a rotatable disc, a caliper straddling aportion of the outer periphery of said disc and movable axially relativeto said disc, friction pad assemblies for engagement with opposite facesof said disc housed in opposed limbs of said caliper and of which one isaxially movable relative to the caliper, actuating means carried by thecaliper for urging said axially movable friction pad assembly intoengagement with one face of said disc, said other friction pad assemblybeing actuated indirectly and urged into engagement with the oppositeface of the disc by the reaction on the caliper of the actuating meansfor said axially movable friction pad, retaining means for at least saidaxially movable pad assembly positioned at each end of said caliperoutside the periphery of said disc, said retaining means including firstand second angularly related abutment faces, lug means at each end of atleast said axially movable pad assembly extending outside the peripheryof the disc and having first and second angularly related facescomplementary to the respective abutment faces of said retaining means,the first of said faces on said retaining means and on said lug meansbeing con structed and arranged to cooperate with each other to take amajor part of the circumferential component of drag at the end of thecaliper with which any part on the disc first comes into alignment, andthe second of said faces being constructed and arranged to cooperatewith each other to take a major part of the radial component of drag atthe opposite end of the caliper, and means for effecting detachment ofsaid lug means from said retaining means, said detachment means beingconstructed and arranged to permit at least said axially movablefriction pad assembly to be removed from the caliper in acircumferential direction relative to the disc.

2. A disc brake according to claim 1 wherein at least the retainingmeans at one end of said caliper comprises plate means.

3. A disc brake according to claim 2 wherein said detachment meanscomprises readily releasable means detachably connecting said platemeans to the end of said caliper.

4. A disc brake according to claim 1 wherein the indirectly actuated padassembly includes lug means co- 6. A disc brake according to claim 5wherein the first A abutment face of said flat plate is substantiallyparallel to the plane of said disc and the second abutment face is atsubstantially right angles thereto and of substantially smaller areathan said first abutment face.

References Cited by the Examiner UNITED STATES PATENTS 2,655,229 10/1953Eksergian 18873 FOREIGN PATENTS 1,229,040 3/1960 France.

785,367 10/1957 Great Britain.

MILTON BUCHLER, Primary Examiner.

G. E. A. HALVOSA, Assistant Examiner.

1. A DISC BRAKE COMPRISING A ROTATABLE DISC, A CALIPER STRADDLING APORTION OF THE OUTER PERIPHERY OF SAID DISC AND MOVABLE AXIALLY RELATIVETO SAID DISC, FRICTION PAD ASSEMBLIES FOR ENGAGEMENT WITH OPPOSITE FACESOF SAID DISC HOUSED IN OPPOSED LIMBS OF SAID CALIPER AND OF WHICH ONE ISAXIALLY MOVABLE RELATIVE TO THE CALIPER, ACTUATING MEANS CARRIED BY THECALIPER FOR URGING SAID AXIALLY MOVABLE FRICTION PAD ASSEMBLY INTOENGAGEMENT WITH ONE FACE OF SAID DISC, SAID OTHER FRICTION PAD ASSEMBLYBEING ACTUATED INDIRECTLY AND URGED INTO ENGAGEMENT WITH THE OPPOSITEFACE OF THE DISC BY THE REACTION ON THE CALIPER OF THE ACTUATING MEANSFOR SAID AXIALLY MOVABLE FRICTION PAD, RETAINING MEANS FOR AT LEAST SAIDAXIALLY MOVABLE PAD ASSEMBLY POSITIONED AT EACH END OF SAID CALIPEROUTSIDE THE PERIPHERY OF SAID DISC, SAID RETAINING MEANS INCLUDING FIRSTAND SECOND ANGULARLY RELATED ABUTMEANS FACES, LUG MEANS AT EACH END OFAT LEAST SAID AXIALLY MOVABLE PAD ASSEMBLY EXTENDING OUTSIDE THEPERIPHERY OF THE DISC AND HAVING FIRST AND SECOND ANGULARLY RELATEDFACES COMPLEMENTARY TO THE RESPECTIVE ABUTMENT FACES OF SAID RETAININGMEANS, THE FIRST OF SAID FACES ON SAID RETAINING MEANS AND ON SAID LUGMEANS BEING CONSTRUCTED AND ARRANGED TO COOPERATE WITH EACH OTHER TOTAKE A MAJOR PART OF THE CIRCUMFERENTIAL COMPONENT OF DRAG AT THE END OFTHE CALIPER WITH WHICH ANY PART ON THE DISC FIRST COMES INTO ALIGNMENT,AND THE SECOND OF SAID FACES BEING CONSTRUCTED AND ARRANGED TO COOPERATEWITH EACH OTHER TO TAKE A MAJOR PART OF THE RADIAL COMPONENT OF DRAG ATTHE OPPOSITE END OF THE CALIPER, AND MEANS FOR EFFECTING DETACHMENT OFSAID LUG MEANS FOR SAID RETAINING MEANS, SAID DETACHMENT MEANS BEINGCONSTRUCTED AND ARRANGED TO PERMIT AT LEAST SAID AXIALLY MOVABLEFRICTION PAD ASSEMBLY TO BE REMOVED FROM THE CALIPER IN ACIRCUMFERENTIAL DIRECTION RELATIVE TO THE DISC.